There has been considerable interest in the hypothesis that some types of psychiatric disorders amy have an infectious etiology. Since Borna disease (BD) virus has a specific affinity for those brain areas thought to be involved with depression (e.g. mesolimbic, hippocampal, hypothalamic, and diencephalic regions) and can produce and observable neurobehavioral syndrome of significantly altered behavioral patterns in laboratory animals, it is uniquely suited to study the viral pathogenesis for some human affective disorders. Moreover, the recent detection of BD- specific antibody in patients with manic depression suggests a possible association of this virus with human affective disorders. BD virus remains poorly characterized. Thus, the aim of this study is to identify an analyze the BD virus genome and to generate BD virus-specific nucleic acid probes which will be used to investigate the prevalence of BD in humans. Specifically, we will isolate BD-specific proteins and after partial amino acid sequencing, prepare cDNA probes from the obtained amino acid sequences; use these cDNA probes, in addition to BD-specific antibody probes to screen lambda gt11 libraries constructed from cells persistently infected with BD virus; generated diagnostic probes form cloned BD antigen-specific cDNA and use them to 1) identify and characterize the BD virus genome, and 2) determine the tissue distribution of BD genome in the BD virus-infected rat, and 3) to investigate whether BD virus is prevalent in humans and associated with particular affective disorders.